Photoflash lamp



Filed Dec, 28 1962 5 7 9 C A k 8 DAVID Y. BROUSE INVENTOR.

ATTORN Y United States Patent 3,158,014 PHOTOFLASH LAlvlP David Y. lirouse, Wiiliamsport, Pia, assignor to Syivania Electriclrotluets Inc, a corporation of Delaware Filed Dec. 28, 1952, Ser. No. 247,803 3 Claims. (Cl; 67--31) This invention relates to the manufacture of photofiash lamps and more particularly to those photofiash lamps in which shredded zirconium foil is employed as the combustible light-producing material, the pressure of the combustion supporting gas is above atmospheric and the volume of the lamp is less than about cc.

In recent years shredded zirconium foil has been used more and more extensively and has gradually replaced shredded aluminum foil as the combustible light-producing material in many photoflash lamps. Concurrently therewith, pressures have increased above atmospheric and lamp volume has decreased. Although, for many years, those skilled in the art considered zirconium and aluminum as substantially equivalent to one another insofar as their use as the combustible light-producing material in photoflash lamps is concerned, it has been discovered more recently that such is not the case. As a matter of fact, it has been discovered that these two materials differ significantly from one another in a number of different characteristics. Some of these differences provide direct advantages attainable when zirconium is used instead of aluminum as the combustible light-producing material. On the other hand, there are other characteristics, which distinguish zirconium from aluminum, which pose cetrain problems in connection with the use of zirconium which were not encountered heretofore when aluminum was used as the combustible.

Some of the physical characteristics of these two materials which difier somewhat appreciably are shredability and shred resiliency. With modern, high speed foil shredding equipment such as that shown in US. Patent 2,699,831 for example, no great difliculty has been experienced in recent years insofar as the shredability of aluminum is concerned. However, with the introduction of zirconium as the preferred combustible material, a substantial difference in shredability was noted and considerable time and effort has been spent in an effort to develop techniques which would insure a good clean cut free of burrs each time a strip of zirconium foil is severed from a large sheet of zirconium foil. It has also been noted that shredded zirconium foil is much more springy than shredded aluminum foil. This undesirable characteristic makes handling of the material during lamp manufacturing operations more diflicult, particularly in view of the trend to smaller and smaller lamp envelopes.

The burning rate of shredded zirconium foil is substantially different from that of shredded aluminum foil; it is appreciably faster. This is an undesirable characteristic in many cases because it results in the maximum light output being reached too early for some types of camera shutter synchronization. One means which has been suggested to overcome this is the use of a slow, low activity igniter system. However, this is not without its drawbacks because low activity igniters are inherently susceptible to erratic, unreliable ignition characteristics. Since the igniter is the combustion initiating source, it is essential that it function effectively even when the battery power source is in a marginal condition.

In view of the foregoing, one of the principal objects of this invention is to improve the above-mentioned physical and performance characteristics of zirconium.

Another of the principal objects of this invention is to improve the above-mentioned physical and performance characteristics of zirconium without adversely affecting other physical and performance characteristics.

3,158,014 Patented Nov. 24, 1 964;

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Other objects, advantages and features are attained in accordance with the principles of this invention by annealing the zirconium foil sufiiciently to cause the development of crystal grains in the material in the range of from about 0.003 to about 0.0006" average diameters. The crystal grain average diameter was determined in accordance with the principles set forth in Methods for Estimating the Average Grain Size of Non-ferrous Metals Other Than Copper and Their Alloys, A.S.T.M. Designation: E91, Plate 1, For U-ntwinned Metals, published by the American Society for Testing Materials. Material with a grain size somewhat below 0.003 tends to have many of the undesirable characteristics of unannealed material, i.e., the cut shreds are very springy and difiicult to handle in lamp making and the combustion rate of the shreds in finished lamps is faster than de sirable when used with an active primer which will provide reliable ignition. Material with a grain size somewhat in excess of 0.0006" crumbles readily when cut'into shreds since the grain size approaches the cross sectional area of the shred. An intergranular boundary extending across the shred cross section results in a cleavage plane which is inherently weak and fractures easily. In extreme cases, shred fractures of this type can be excessive,

causing the formation of many fragments. These fragments, due to their small size, are light, freely airborne, and likely to collect in areas surrounding the shred cutting equipment causing a fire hazard. Due to the extremely combustible nature of zirconium, accumulations of small particles are most dangerous.

In the accompanying drawing, the single figure illustrates one type of photoflash lamp with which this invention may be employed. The lamp comprises a sealed light-transmitting envelope 1 having a volume of about 1.2 cc., within which about 27 milligrams of shredded zirconium foil 3 is disposed. The envelope 1 is provided with a filling of combustion-supporting gas, such as oxygen for example, at a pressure of about 440 cms. Hg. A filament 5 is disposed within the envelope 1 and is attached to lead-in wires 7 and 9 which are supported by and extend through insulator button 8. The inner ends of the lead-in wires 7 and 9 are provided with a quantity of ignition paste 11. The lead-in wires 7 and 9 extend through an end of the lamp envelope and are bent into the form of stirrups 13 and 15 lying along opposite sides of the press 17, the wires finally re-entering the press 17 some distance away from the points at which they emerge. The stirrups l3 and 15 define electrical contact members for engagement with electrical contact members of a flashgun.

Tests were made, using annealed and unannealed zirconium foil, with lamps of the type just described and the following results were obtained:

Photometric results Peak Total Etficiency time output (lumen- (m1llisec.) (lumensee/mg.) sec.

Shred width (inches) Foil Foil condition thickness (inches) Unannealed Annealed Unannealed- MOOOEDbmomentum sow-\rsow Unannealed Annealed employed as the combustible material in photoflash lamps. The time to peak has been lengthened, on the average, by about 20%. Thus the slower combustion rate of annealed zirconium makes possible the use of a more active and hence a more reliable igniter than can be used with unannealed zirconium.

A noticeable improvement in physical characteristics is obtained with the annealed Zirconium. Its shredability is improved and its springiness diminished.

Most unexpected was a substantial incerase in light output and efliciency with the annealed zirconium foil. As the above table indicates, these performance characteristics were improved, on the average, by over 10%.

Similar performance improvements may also be obtained with another family of pliotoflash lamps identified commercially as M3, M5 and M25. A T6 /2 bulb is employed in the manufacture of these lamps and the sealed envelope has a volume of about 7.5 cc. These lamps are provided with a filling of about 41 milligrams of shredded zirconium foil and a combustion supporting gas, such oxygen for example, at a pressure of about 120 cms. Hg. The data developed in tests with these lamps are as follows:

1. A photofiash lamp comprising: a sealed light-transmitting envelope; at combustion-supporting gas filling in said envelope; a quantity of filamentary zirconium disposed in said envelope, said zirconium being characterized by crystal grains in the range of about 0.0003 to about 0.0006" average diameters; and ignition means disposed in said envelope in operative relationship with respect to said filamentary zirconium.

2. A photoflash lamp comprising: a sealed light-transmitting envelope; a combustion-supporting gas filling in said envelope at a pressure above atmospheric; a quantity of filamentary zirconium disposed in said envelope, said zirconium being characterized by crystal grains in the range of about 0.0003" to about 0.0006" average diameters; and ignition means disposed in said envelope in operative relationship with respect to said filamentary zirconium.

3. A photoflash lamp comprising: a sealed light-transmitting envelope having a volume of less than about 10 cc.; a combustion-supporting gas filling in said envelope at a pressure of at least several atmospheres; a quantity of filamentary zirconium disposed in said envelope, said zirconium being characterized by crystal grains in the range of about 0.0003" to about 0.0006 average diameters; and ignition means disposed in said envelope in operative relationship with respect to said filamentary zirconium.

References Cited by the Examiner UNITED STATES PATENTS 2,136,234 11/38 Cartun 67-3l 2,177,108 10/39 Highriter 6731 2,254,849 9/41 Kriedler 67-31 2,272,779 2/ 42 Sarbey 67-3l 2,982,119 5/61 Anderson 67-31 3,114,250 12/ 63 Desaulniers 67-3l EDWARD J. MICHAEL, Primary Examiner. 

1. A PHOTOFLASH LAMP COMPRISING: A SEALED LIGHT-TRANSMITTING ENVELOPE; A COMBUSTION-SUPPORTING GAS FILLING IN SAID ENVELOP; A QUANTITY OF FILAMENTARY ZIRCONIUM DISPOSED IN SAID ENVELOPE, SAID ZIRCONIUM BEING CHARACTERIZED BY CRYSTAL GRAINS IN THE RANGE OF ABOUT 0.0003" TO ABOUT 0.0006" AVERAGE DIAMETERS; AND IGNITION MEANS DISPOSED IN SAID ENVELOPE IN OPERATIVE RELATIONSHIP WITH RESPECT TO SAID FILAMENTARY ZIRCONIUM. 